Dodgy physics

[arizonachris]

Nick, SPAD is "Signal Passed at Danger" In RW, sometimes you will get a red signal. Press the "TAB" key and RW will either let you pass the red without a derail, or it will say "Request to pass at SPAD denied" You will derail (game over! ) if you don't get permission to go thru the red by the dispatcher.

[Kali]

Chris: depends on how a car is set up whether it being loaded or not makes a difference. If the cars are set up properly in the load section you will most definitely find a difference in consist weight if you load it. Unfortunately the brake force doesn't change, either you compromise and set the brakes up for fully loaded, or you have empty and loaded versions of a car which rather destroys the point in having it loadable in the first place.

Nick: ok. Midday, it's 95F, the rails are dry and clean, there' s no wind to speak of, the route is a little curvy but averages 1.8-2%, the cars are all fully loaded with 95 tons of coal and they've all come out of the shops pretty recently so the rigging is well adjusted, the hoses don't really leak and the shoes aren't worn. You are halfway down the hill so your train pipe has had some time to equalise and your slack has also equalised somewhat. The current route speed limit is 30mph.

Pick your speed, pick some sort of representative pressure you'd expect to have on, and then pick some sort of distance you'd expect to haul up if you had to stop & went to full service. I am basically looking for a representative number to throw in cars that won't over or underbrake them, so you can start using more realistic ideas for train control. I can't do variable brake settings on individual cars using the same blueprint, it just won't let you do that. You can randomise it slightly across reskins of course, but you don't want 100 different coal car variants just for one consist...

Tabbing past a red will work if the route itself isn't blocked ( ie, the physical route is set in your direction ); that's an allowable movement in the UK if you stop and ring the signaller first. You shouldn't game-over on a SPAD unless you tick the options box for it; what will probably happen is you'll trigger an emergency stop which might well derail you with the way it is atm.

[TrainMaster1]

Well you did not tell me how many cars in the train unless I missed that...which would not surprise me so here are some tid bits out of my old qualification manuals.

BRAKE RELEASE TIME AFTER EMERGENCY APPLICATION

Except when it is known that the brakes have released, before any attempt is made to start a train, sufficient time must be allowed for the
air brakes to release on the entire train. Average release time for a freight train if the brakes have been previously applied in full service
application is 2 minutes for 100 cars, 4 minutes for 150 cars and 6 minutes for 200 cars. Add 2 minutes to these times if brakes have been
applied in emergency.

EMERGENCY BRAKE APPLICATION
When the speed of train cannot be controlled properly from use of the dynamic and/or service brake application, an emergency brake
application must be initiated without hesitation. NOTE: Any train descending a grade of 1% or greater over a distance of 3 continuous
miles must be immediately brought to a stop by an emergency brake application, if necessary, when the movement exceeds the maximum
authorized speed at that location by more than 5 MPH.

A running release must not be made after an emergency brake application. When the PC switch activates following an emergency
application, the automatic brake valve must be placed in emergency position and left in that position until the train stops.
When employees are positioned at the rear of a moving train and radio communication is available, the Engineer in control of the train
must be notified immediately when the air brakes are applied:
• in emergency from the rear end of the train
• due to an emergency brake application
When so notified, the Engineer in control of the train must immediately
place the automatic brake valve in the emergency position.
When an emergency brake application occurs, the locomotive
brake(s) must be bailed off if the locomotive(s) is in “power throttle” to
prevent jackknifing the train.

If an emergency brake application occurs while in dynamic braking, the independent brake must be bailed off to prevent excessive
braking forces or sliding locomotive wheels. When train speed reduces to the point where the dynamic brake is no longer effective, the independent
brake should be applied to a safe level to prevent train slack from running out as the train comes to a stop. Care must be taken
to prevent excessive braking forces and to prevent locomotive wheels from sliding.

If operating light locomotive(s) and an emergency brake application occurs while in dynamic braking, the independent brake may be used to bring the locomotive(s) to a safe stop. The Engineer must be aware that when using the independent brake and brake cylinder pressure is
15 pounds or greater, extended range dynamic braking is nullified thus reducing effective dynamic braking force at low speeds. Care must be
taken to prevent locomotive wheels from sliding.

SERVICE BRAKES: This is the type of brake application normally used for braking. This level of braking is achieved with a 6psi to a 26psi reduction in the brake pipe pressure. When the AB valve senses the difference in pressure air is ported from the reservoir to the brake chamber. Air pressure acts against the diaphragm and brakes are applied. Braking with the Service Brakes offers up to 75% of a train's Emergency Brake capability.

INDEPENDENT BRAKES: These are the brakes on the locomotive units only and do not apply brakes on any of the cars. While this brake method would effectively slow the locomotives if operated alone, this type of braking has only a minimal effect on a fully loaded train. These brakes are used in train handling, standing or any time a small brake level is needed on a train. They can give a braking level from none up to full independent, which is 75% of the locomotive's Emergency Brake capability. (Oh and to answer any earlier question...they should apply to all locos in the real world. Most sims only seem to get these to the first loco.)

POWER BRAKING: This means just what it says. When an engineer anticipates a problem may develop or desires to control the speed of the train, an application of the service brakes is made without reducing the throttle. When the train has slowed or the problem does not arise, then the train brakes are released and the train continues on, with the throttle still set. This type of braking has the advantage of reducing the time necessary to achieve Emergency Braking. This results in a quicker stop than an Emergency stop that was not preceded with Power Braking.

DYNAMIC BRAKES: Dynamic braking is using the traction motors of the units in a reverse flow so that they act to stop or slow the train. This type of braking is used primarily for train handling as it only slows the train via the locomotives. This type of braking cannot compare to train brakes.

EMERGENCY BRAKES: This is all the brake capability that a train has. It is utilized, as implied, when there is an emergency. Application of Emergency opens the brake pipe to atmosphere on all cars and units sequentially from front to rear. As a result, the AB Valves ports pressure from the Emergency reservoir to the brake chamber and all brakes slow the train. This type of brake use applies the brakes as fast as possible. An emergency application will cancel throttle to idle (see Power Braking above).

Still awake? Try this link....citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.19.5494.pdf

Hope this helps....

Special Note for Chris: We have found a way around this (SPAD) in MSTS. If you are in free roam and not running a scenario (which is what we will do in our sessions). Can you then go past a signal without penalty. In MSTS we use explore route and get past any signal we need to. Our live DS is what guides the session not some poor guy trapped in your hard drive. No wonder he rarely says yes...it's cramped in there and he's cranky.

Nick

[Bart35]

Kali.. Thanks for the brake file works great!! would it be possible to add it to the rest of the sd-40??

[Kali]

80 cars, ~120t total weight each ( was in a previous post, I should have put it all together in one ).

I might actually be able to do something about the variable release time, but it will only work with certain stock - ie a wagon script I provide. You will probably not want to use the auto brake for light engine work ( and I'm not terribly sure about short consists either ) but we'll see if it's usable - if it's not then we pick something reasonable instead. Good info though, cheers.

Chris, I'll probably produce a kit and instructions once the bugs are worked out - it would not take very much editing though.

[arizonachris]

Hey, I just figured out, I'm a "Dynamic Breaker"! That's how I always run, unless I'm coming up to a stopping point. always a little throttle, and a little brake. Modulate back and forth depending on grade, etc. Cool!

Nick, if you un tick the box in RW's settings that says "Exit on SPAD", like Kali said, you will not get a derail or "game over" if you decide to blow thru the red. The 9 key will always show you the path ahead thru the switch and will show any train that might be blocking you. At times the red is for a reason, at times it's a glitch.

Kali, like Bart said, the script works fine. Maybe a little too well. I took 3 CN SD40's on Rich Garber's Fort Kent route (one of my favorites) with 60 double stack intermodals. I like that route because it's nice and flat. Mostly. Braking was what I was used to, -10mph per .1 miles. Now, bring on the black SD40's, 3 of them, same consist. Wow! Wheel slip! Derailed it. Looked like an accordian. So for me, it's too strong, or I just need to relearn braking with all the engines doing braking. But, using the train brake alone RW doesn't seperate the engines from the consist, like all those cool handles and valves that Nick was talking about.

Nick, also, all that cool info about brake pressure recharge times, in Railworks, it's about 1 second, maybe 2 at the most. 2 minutes? 4 minutes? Hah! Never. There is a difference when you hit the "Backspace" key (Emergency) which makes the train come to a complete stop before you can resume, or using the ; and ' keys to apply emergency, which you can just release and go about your merry way without a complete stop.

[TrainMaster1]

Chris: Just another of the many differences of running a railroad and playing a game. There are many things from having your conductor go to the ground to work cars 30 or more deep in your train, to brake loading times and lots more that most people think are "annoying." To do it right requires not just skill but patience to learn the ropes and wait to "simulate" how that would happen in the real world.

BTW, I asked about SPADS because when we launch our RW sessions in November we need a way to have everyone run under dispatcher control so we need the ultimate in free roam ability so that the DS can direct traffic as needed and not dictated by the game. When we run there are no activities or scenarios to worry about. It is just you, your prototypical train (we tell you the engines and cars needed to mirror the real train) and your skills. You will be running an actual train from the day we are recreating with correct symbol, work orders, etc. for that route in the session.

Hoping that a few good RW engineers are willing to learn the ropes and join us on November 3rd for the next Intro Event and really learn what a sim can do when you understand the operations behind it all. People who attend the events on 11/3 and 11/6 are eligible to run in our first two RW minis coming up later in November.

Thanks,

Nick

[Kali]

If the DB are too strong now then that's a problem with the original SD40 rather than the script using all of the head units - and I think they might be seeing as with the cars I'm trying to set up, the DB is stronger than the auto brake... The auto brake release on those SD40s is ~45s for a full release which is what we use over here for slower freight, which would be about right for 60ish cars, it seems. I haven't touched the DB settings at all other than to notch the handle. Without having any idea of how they're meant to be I'm rather loathe to go poking around, either.

I still need to know if the driver of the consist I detailed yesterday would allow half a mile or 6 miles to stop at full service, and/or the same for emergency, I don't even know that much.

[TrainMaster1]

Here's an example of a smaller and lighter train on virtually flat ground.

Total Available Distance = 485'

Initial speed = 29 M/H (42.5 ft/sec)

Estimated reaction time = 1.5 Seconds

TRAIN DATA
Number of units (Locomotives) = 2
Length of units (Locomotives) = 136.66 feet
Weight of units (Locomotives) = 350.5 tons
Number of cars = 18
Length of cars = 902 feet
Gross weight of cars = 980 tons
Empty weight of cars = 540 tons
Train length = 1038 feet
Gross weight of train = 1330 tons
Empty weight of train= 890 tons
Brakepipe pressure= 90 psi
Emergency propagation= 1.128 sec.
Emergency braking efficiency= 0.736
Grade= -.00173

First lets determine the Engineer's reaction distance using an average reaction time of 1.5 seconds.

Reaction distance = (Reaction Time) x (Speed)

Reaction distance = (1.5 seconds) x (42.5 ft/second) = 64 feet.

Subtracting this reaction distance from the total distance of 485' leaves 421' feet for the train to slow.

Next let's determine how long it would take the train to arrive at the crossing if the engineer did not act.

Distance/Rate = Time

(421 feet) / (42.5 ft/second) = 9.89 seconds

Next, we must calculate the actual slowing for the train. This is not a simple calculation. Recall we must account for the time for the air to propagate the length of the train. Next, the actuation time of the brakes for each car must be considered. We must also determine the weight of the train then compare it to brake force. The results of these calculations will be presented in the table below without support.

Initial Speed is 29 mph

Stopping Distance: 712.1

Time to Stop :25.89

The first thing that is apparent is that the available stopping distance of 421' is well less than the 712.1' feet required for the train to stop. The conclusion: The train can't stop before it gets to the crossing. But perhaps more interesting is the comparison of the time it takes the train to reach the crossing with and without braking. Again, this involves detailed calculations beyond the scope of this treatment. The result will be presented for purposes of comparison. Given the 421' brake distance the train arrives at the crossing at 24.14 M/H. The time it arrives is 10.46 seconds after the point the brakes were first applied. This time should be compared to the time required to reach the crossing if no action was taken. That time calculated above was 9.89 seconds. The difference is .57 seconds. This difference in time is not much, but perhaps sufficient for one additional car to make it across the crossing.

The article link I sent yesterday should contain the formulas you need to actually calculate any situation. An 80 car train on a 2% grade will take well over a mile to come to a complete stop. That is why crossing jumpers and pedestrians rarely win the argument. Coal Loads are more forgiving than liquid loads or loads that bulkheads which present different concerns.

Nick

[Kali]

Ah, that link just got me "No document with DOI "10.1.1.19.5494.pdf" -The supplied document identifier does not match any document in our repository." unfortunately, so I left it be ( and forgot to search for it :p ).

"Well over a mile" is a good starting point though, there's no way we're going to get this particularily accurate.

[Dan]

To change the subject slightly, I had a very interesting experience yesterday when travelling home. The train failed completely with a loss of electrical power, so we had to be rescued and then propelled to our final destination.

What was interesting was how long it took for the rescue train to come up behind us and also all the safety practices that were built into the procedure that you would struggle to replicate in a sim. The Guard had had to go back and protect the train (I know this because I heard the detonators go off as the rescue train approached. It struck me that what in a sim would be presented as quite a simple act - ie go rescue a broken down train and then propel it to its final stop is in fact a very complex operation simply because of safety etc.

[TrainMaster1]

Yes it is not easy and we have done that in our sessions already when we had a conductor under rule 99 walk back and protect the end of his train. We did this because that is what would have been done in the actual real world situation. As the dispatcher on duty in that session, it was my duty to make sure the train was protected and the following traffic notified of the danger ahead. Now was the train really in danger of being hit from behind? No...but it adds the element of realism that we look for in operating sessions. The road we were on and the time era we were running in dictated that the train be protected so we did. Right down to the "placement of torpedoes and lighting of fusees" at the proper distance.

This probably would not be done for one person running a scenario on their own but we have 20+ crews and trains to protect so we do what we have to get it done right by the book.

Nick

[Chacal]

Right down to the "placement of torpedoes and lighting of fusees" at the proper distance.

His wife must have been pi**ed at him lighting fusees in the computer room.

[TrainMaster1]

Never though of asking him how the "virtual" family responded to that....but then they would have been many miles from trackside in their "virtual" home. Our emphasis is always on running a railroad...the game is completely secondary.

Nick

[Toripony]

Too bad I missed it. Sorry guys, I was busy with home packing/moving. Wow, what a great discussion... I've tried to read most of the posts to catch up and learned a lot. I downloaded the SD40 brake test model; will try it out as soon as I find time.

Question: How does your modd compare with the modd that RWTools applies now? I have that applied to all of my diesel repaints now and I like that it allows me to set as little as 3 lbs of pressure, more often I use 6-10. I understand from the discussion the true pressure should be 7 lbs but the braking parameters on the freight (and passenger?) cars is incorrect.

One thing I didn't understand was a discussion about the minimum being correct at 7 lbs upon first application... but mine runs up to 14 lbs, and some of the newest units with TS'12 run up to 17 lbs as soon as I reach 30% on the brake lever????? (and the train comes to a ridiculously fictitious stop). What did I miss there????

What this thread needs now is a summary..... anybody? What were your final findings/conclusions and should we just accept what RSC is doing or make a bigger case out of improving the brake realism? And after all the discussion of how the brakes should be set and how I should be using them, I am totally confused . Can anyone sum it up for me/us from the perspective of driving in TS/RW? While I do want to create some realism when possible, I don't want to go to extremes trying make everything perfectly real. Some of this game is about using our imaginations!

BTW, the rules for the EB Alleghany sub grade calls for 6 lbs of brake reduction for the entire 25 mile journey (prior to 1995; I don't know today's rules). My reason for this whole topic has been that using default RSC stock I cannot comply with that rule (not without employing some very unrealistic jockeying of the brake handle).

Thanks for a fascination read! Makes me think we should have a "U.S. Brakes" committee or something.